We know that what happens in the mouth doesn’t stay in the mouth – but the connection of the oral cavity with the rest of the body goes well beyond chewing, swallowing, and digestion.
The healthy human oral microbiome consists not only of clean teeth and firm gums, but also of energy-efficient bacteria that live in an environment that is rich in blood vessels and enables the organisms to communicate constantly with cells and proteins of the immune system.
A growing body of evidence has shown that this system, which seems so disconnected from the rest of our bodies, actually has a huge impact on and is influenced by our overall health, said Purnima Kumar, professor of periodontics at Ohio State University , at a science conference this week.
For example, it has long been known that type 2 diabetes increases the risk of gum disease. Recent studies showing how diabetes affects the bacteria in the mouth explain how treating periodontal disease, which changes oral bacteria, also reduces the severity of the diabetes itself.
Associations have also been found between oral microbes and rheumatoid arthritis, cognitive skills, pregnancy outcomes, and heart disease, supporting the belief that an unhealthy mouth can go hand in hand with an unhealthy body.
What happens in your body affects your mouth, and that in turn affects your body. It really is a cycle of life. “
Purnima Kumar, Professor of Periodontics at Ohio State University
When the American Association for the Advancement of Science (AAAS) addressed this year’s annual meeting on dynamic ecosystems, Kumar saw the opportunity to put the mouth on the map as a living microbial community that can tell us a lot about ourselves.
“What’s more dynamic than the gateway to your body – the mouth? It’s so ignored when you think about it, and it’s the forward-facing part of your body that is in contact with the environment, and it’s with this entire tube system connected. “She said. “And yet we study everything except the mouth.”
Kumar organized a session at the AAAS meeting today (February 8, 2021) entitled “Killer Smile: The Link Between the Oral Microbiome and Systemic Diseases”.
The oral microbiome refers to the accumulation of bacteria – some helpful to humans and some not – that live in our mouths.
Kumar led and collaborated on recent research that further elucidated the relationship between oral health and type 2 diabetes, first described in the 1990s. She was the lead author of a 2020 study comparing the oral microbiomes of people with and without type 2 diabetes and how they responded to non-surgical treatment for chronic periodontal disease.
The team found that periodontal disease allows bacteria – and not the human host – to take over the reins in determining the mix of microbes and inflammatory molecules in the mouth. Treatment for gum disease eventually restored a normal host-microbiome relationship, but more slowly in people with diabetes.
“Our studies have concluded that people with diabetes have a different microbiome than people who are not diabetic,” said Kumar. “We know that changing the bacteria in your mouth and restoring the bacteria your body knows as healthy and friendly bacteria actually improves your blood sugar control.”
Although much remains to be learned, the fundamentals of this relationship between the oral microbiome and systemic disease have become clear.
Oral bacteria use oxygen to breathe and break down simple molecules of carbohydrates and proteins to stay alive. Something as simple as not brushing your teeth for a few days can trigger a cascade of changes that stifle oxygen supply and cause microbes to enter a fermentative state.
“This creates a septic tank that produces by-products and toxins that stimulate the immune system,” said Kumar. This is followed by an acute inflammatory response that produces signal proteins that bacteria consider food.
“Then this community shifts – it’s an ecosystem – organisms that can break down protein grow more, and organisms that can breathe in an oxygen-deprived environment grow. The bacterial profile and, most importantly, the function of the immune system change.” She said .
The inflammation opens the pores between the cells that line the mouth and leaks the blood vessels, allowing the unhealthy bacteria to circulate throughout the body.
“The body creates inflammation in response to these bacteria, and these inflammatory products also go into the bloodstream. Now you are being hammered twice. Your body is trying to protect you and turn on itself,” said Kumar. “And these pathogens have a field day and cross boundaries they should never cross.”
The exact mechanisms of the links between the oral microbiome and certain diseases are complex and still being studied, but the secret to a healthy mouth is no secret at all: preventing oral disease is as simple as brushing and flossing and visiting the dentist twice a year for one professional cleaning, said Kumar.
The U.S. Surgeon General’s Office announced in 2018 that it had commissioned an update to its 2000 oral health report, which was the first to be published on the subject.
Kumar said that the national emphasis on oral health as an integral part of general wellbeing supports her argument that the mouth should be an “equal opportunity player” in determinants of health.
“Put my mouth back in my body – that’s my goal here,” she said.
Kumar, PS, et al. (2020) Subgingival Host-Microbial Interactions in Hyperglycemic Individuals.
Journal of Dental Research. doi.org/10.1177/0022034520906842.